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B-cell lymphoma of the brain in a patient with (autopsy-proved) AIDS. The delineation and conspicuity of the highsignal-intensity lesions in the bilateral posterior fossa (arrows) are equal on both T2-weighted fast spin-echo (3752/120/4) (A) and FLAIR fast spin-echo (7000/ 150/4; inversion time, 2100) (B) MR images.
Source publication
To compare the value of fast fluid-attenuated inversion-recovery (FLAIR) with T2-weighted fast spin-echo MR imaging in the detection of acquired immunodeficiency virus (AIDS)-related lesions of the brain.
Forty-four human immunodeficiency virus (HIV)-positive patients were examined with both sequences on either a 1.0-T or a 1.5-T MR system. The num...
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Citations
... Generalized brain atrophy is the most common imaging finding. MRI may show patchy T2W/FLAIR hyperintensities in periventricular and subcortical white matter, which tends to be more diffuse and confluent with disease progression (Fig. 9) [38]. Lack of brain parenchymal or meningeal enhancement differentiates it from other opportunistic infections. ...
Dementia is defined as chronic deterioration of intellectual function and cognitive skills significant enough to interfere with the ability to perform daily activities. Recent advances in the treatment of dementia have renewed interest in the use of various neuroimaging techniques that can assist in the diagnosis and differentiation of various subtypes. Neuroimaging and computational techniques have helped the radiological community to monitor disease progression of various neurodegenerative conditions presenting with dementia, such as Alzheimer disease, frontotemporal lobe dementia (FTLD), progressive supranuclear palsy (PSP) and multisystem atrophy-cerebellar variant (MSA-C), and their response to newer therapies. Prompt identification of treatable or reversible forms of dementia, such as tumours, subdural haemorrhage and intracranial dAVF, is crucial for the effective management of these conditions. It is also prudent to recognize the imaging spectrum of metabolic, infective and autoimmune diseases with rapidly progressing dementia, such as methanol toxicity, central pontine myelinolysis (CPM), delayed post hypoxic leukoencephalopathy (DPHL), HIV, Creutzfeldt-Jakob Disease (CJD), Sjogren's syndrome, multiple sclerosis (MS), radiation necrosis and Fragile X-Associated Tremor/Ataxia Syndrome (FXTAS), which are difficult to treat and often require palliative care. This pictorial review emphasizes various non-Alzheimer’s dementia entities and discusses their imaging highlights.
Teaching Points
• Non Alzheimer’s dementia constitutes a broad spectrum of conditions.
• Neuroimaging plays an important role in differentiating treatable from irreversible dementia.
• Neuroimaging is often non-specific in early stages of neurodegenerative conditions with dementia.
• Neuroimaging plays an important role in the multimodal approach towards management of dementia.
... The T2-weighted FLAIR sequence has been shown to be the single most sensitive sequence for the detection of brain pathology [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Saleh et al. demonstrated in 1026 consecutive outpatient MRI studies that this sequence alone had positive and negative predictive values of 96.1% and 98.4%, respectively, for lesions detectable by a complete MRI protocol that included contrast enhancement [17]. ...
Background/Purpose
Patients with neurologic complaints are imaged with MRI protocols that may include many pulse sequences. It has not been documented which sequences are essential. We assessed the diagnostic accuracy of a limited number of sequences in patients with new neurologic complaints.
Methods
996 consecutive brain MRI studies from patients with new neurological complaints were divided into 2 groups. In group 1, reviewers used a 3-sequence set that included sagittal T1-weighted, axial T2-weighted fluid-attenuated inversion recovery, and axial diffusion-weighted images. Subsequently, another group of studies were reviewed using axial susceptibility-weighted images in addition to the 3 sequences. The reference standard was the study's official report. Discrepancies between the limited sequence review and the reference standard including Level I findings (that may require immediate change in patient management) were identified.
Results
There were 84 major findings in 497 studies in group 1 with 21 not identified in the limited sequence evaluations: 12 enhancing lesions and 3 vascular abnormalities identified on MR angiography. The 3-sequence set did not reveal microhemorrhagic foci in 15 of 19 studies. There were 117 major findings in 499 studies in group 2 with 19 not identified on the 4-sequence set: 17 enhancing lesions and 2 vascular lesions identified on angiography. All 87 Level I findings were identified using limited sequence (56 acute infarcts, 16 hemorrhages, and 15 mass lesions).
Conclusion
A 4-pulse sequence brain MRI study is sufficient to evaluate patients with a new neurological complaint except when contrast or angiography is indicated.
... Compared with the postmortem studies, MR imaging underestimated the presence of HIV-related lesions in the brain [23]. Fluid-attenuated inversion recovery (FLAIR) techniques have been shown to improve conspicuity of the lesions in the periventricular and subcortical locations significantly [24]. The data from recent studies suggest that proton ( 1 H) magnetic resonance spectroscopy (MRS) could potentially be more sensitive in detecting early CNS involvement by HIV than MR imaging [25][26][27][28][29][30][31][32][33][34][35][36][37]. ...
The brain may be affected by a variety of abnormalities in association with HIV infection. Knowledge of these abnormalities and their characteristic imaging features is important to neuroradiologists for the detection, diagnosis, and initiation of appropriate treatment. This review attempts to describe the imaging findings associated with brain disorders in HIV-seropositive patients and the rationales for integrating neuroradiologic techniques.
... The accuracy of fluid-attenuated inversion-recovery (FLAIR) sequences as compared with that of T2weighted spin-echo (SE) MRI has been tested in a wide variety of brain diseases, such as multiple sclerosis [1, 2], infections [3,4], brain neoplasm [5-7], hypoxic-ischemic encephalopathy [8], stroke [9, 10], hypertensive encephalopathy/reversible and posterior leukoencephalopathy syndrome [11]. This sensitivity is related to the capability of detecting lesions causing T2 prolongation associated with nulling of normal cerebrospinal fluid (CSF) background, leading to high lesion/tissue contrast [10]. ...
We investigated the accuracy of MRI in the early diagnosis of infectious meningitis with emphasis on the value of gadolinium-enhanced fluid-attenuated inversion recovery (FLAIR) sequence. Twenty-seven patients with clinical suspicion of infectious meningitis were included. MRI was performed within 3 h of clinical evaluation. For all patients, T1-weighted spin-echo, dual-echo T2-weighted fast-spin-echo and FLAIR sequences were performed, followed by gadolinium-enhanced T1-weighted spin-echo and FLAIR sequences. Final diagnosis was based on the clinical findings and the analysis of cerebrospinal fluid, obtained by lumbar puncture after the MRI. Infectious meningitis was confirmed in 12 patients. In all of these patients of the plain studies, FLAIR was positive in only four patients. MRI gadolinium-enhanced FLAIR showed abnormal meningeal enhancement in all 12 patients, while gadolinium-enhanced T1-weighted spin-echo was positive only in six cases. There were no false-positive or false-negative results. It is concluded that MRI could have an important role in the early screening for infectious meningitis, provided a gadolinium-enhanced FLAIR sequence is used.
... The nulling of the CSF maximizes the sensitivity of the sequence to changes in the T 1 relaxation time of CSF. Many reports confirm the superiority of the FLAIR sequence over conventional spin-echo (SE) sequences with respect to disease in the subarachnoid space and parenchyma [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. It has been suggested that FLAIR images may eliminate the need for gadolinium enhanced T 1 weighted images in the diagnosis of leptomeningeal disease [18] and in the detection, but not characterization of, intracranial tumours [19,20], intracranial infections [21], multiple sclerotic lesions [22], and others [1]. ...
... Many reports confirm the superiority of the FLAIR sequence over conventional spin-echo (SE) sequences with respect to disease in the subarachnoid space and parenchyma [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. It has been suggested that FLAIR images may eliminate the need for gadolinium enhanced T 1 weighted images in the diagnosis of leptomeningeal disease [18] and in the detection, but not characterization of, intracranial tumours [19,20], intracranial infections [21], multiple sclerotic lesions [22], and others [1]. ...
... Additionally, the nulling of the highest signal (fluid) improves the apparent contrast between white matter, grey matter, and lesions due to a better use of the dynamics (highest signal intensity minus lowest signal intensity) during acquisition. Thus, FLAIR imaging has been found to be more sensitive than other sequences in the evaluation of cerebral pathology [1][2][3][4][5][6][7][8][9][10][11][12]. After FLAIR images give an overview of the pathology, the further examination can be adapted accordingly. ...
We hypothesized that in patients with negative fluid-attenuated inversion recovery (FLAIR) images T(2) weighted fast spin-echo (FSE) images and T(1) weighted spin-echo (SE) images before and after intravenous administration of gadolinium-based contrast medium display no pathology either. Thus, we assessed the negative predictive value of FLAIR images to rule out MR-detectable brain lesions. 1026 consecutive cranial MR examinations were reviewed. Routine MRI of the brain included T(1) weighted coronal imaging before and after administration of gadopentetate dimeglumine, axial T(2) weighted FSE and fast-FLAIR imaging. The FLAIR images were rated by two radiologists into categories of 0 (without pathologic changes) and 1 (with pathologic changes). Two other radiologists analysed the complete examination. In 284 MR examinations of the brain no abnormalities were found (28%). FLAIR-ratings were false-negative in four cases and false-positive in 30 cases. Sensitivity and specificity of the FLAIR sequence for MR-detectable brain lesions were 99.5% and 89.4%. The unselective application of gadolinium avoided one false-negative MR-reading and improved the sensitivity of the MR-examination from 99.5% to 99.6%. Positive and negative predictive values were 96.1% and 98.4%, respectively. The interobserver reliability was kappa=0.93 for the FLAIR-readers and 0.89 for the readers who rated the complete examination. In conclusion, negative FLAIR images provide a high negative predictive value for MR-detectable brain lesions. Thus, in patients with negative FLAIR images the unselective application of gadolinium seems to be unnecessary.
... The usefulness of FLAIR as compared with T2weighted spin-echo MR imaging has been tested in a wide variety of brain diseases, including stroke [2,3], multiple sclerosis [4,5], infections [6,7], hypertensive encephalopathy/reversible posterior leukoencephalopathy syndrome [8], brain neoplasms [9,10,11], and hypoxic-ischemic encephalopathy [12]. ...
Fluid-attenuated inversion recovery (FLAIR) sequence is currently used in clinical practice. Some reports emphasize the possibility that, in pathologic conditions, intravenous injection of gadolinium chelates may lead to an increased signal inside the cerebrospinal fluid (CSF). The aim of this study was to evaluate the presence of CSF signal changes in pathologic conditions causing blood-brain barrier disruption or neovascularization when imaging is performed after intravenous injection of gadolinium. We obtained FLAIR sequences after gadolinium injection from 33 patients affected by different intracranial pathologies and 10 control subjects. Patients were affected by ischemic stroke in the subacute phase, from 2 to 7 days from onset of symptoms (12 patients), meningiomas (8 patients), high-grade gliomas (5 patients), previous surgical procedures for intra-axial neoplasms (5 patients), and multiple sclerosis with active plaques (3 patients). Magnetic resonance imaging was performed in patients and controls using a 1.5-T magnet, using T2- and T1-weighted FLAIR sequences. The FLAIR sequence was acquired before and 1-3 h after injection of a standard dose of gadolinium. In those patients affected by ischemic lesions, FLAIR sequences were repeated the next days and 3-4 days later. The CSF signal was visually evaluated by two readers and scored from 0 to 3 depending by the degree of enhancement. The location of CSF signal changes (close to the lesion, hemispheric, or diffuse) was also considered. The CSF signal was markedly increased after 3 h from intravenous injection of gadolinium in all the patients with stroke, in those with previous surgery, and in those with high-grade gliomas whose neoplasm's surface was in contact with the subarachnoid spaces (SAS) or ventricles; a strong enhancement was also evident inside the necrotic component of the tumor. The CSF changes were more evident close to the pathology and/or in the hemisphere involved by the pathology. Moderate CSF enhancement was observed in the SAS close to meningiomas. No signal changes were evident in all the others. In those patients with stroke imaged in the following days, CSF signal showed to be diffuse to both hemispheres the next day and returned to normal values within 2 days. In patients affected by pathologies with blood-brain barrier breakdown or neovascularization close the SAS or the ventricles, CSF changes, related to gadolinium leakage, are likely when FLAIR sequences are acquired 2-24 h after i.v. injection of the contrast. This pattern should be known in order to differentiate it from that of subarachnoid hemorrhage.
... Less common findings are basal ganglia lesions and small white matter lesions. FLAIR (fluid attenuated inversion recovery) sequences are useful for detecting the latter [5] and for distinguishing them from non-specific T2 hyperintensities predominantly caused by prominent perivascular spaces. ...
Human immunodeficiency virus (HIV) is neu- rotropic and crosses the blood-brain barrier at an early stage in the disease. Thus, the central nervous system (CNS) is a major target of HIV, with approximately two-thirds of patients devel- oping CNS involvement during the course of their disease. The spectrum of CNS disease in acquired immune deficiency syndrome (AIDS) is wide and can be broadly categorized into primary effects of HIV, opportunistic infections, neo- plasms and vascular disease. Clinical findings are non-specific, and are often unhelpful in distinguishing between the vast array of neurological disease processes in AIDS. They may range from mild cognitive impairment to frank neurological deficit and, in extreme cases, coma. Since clinical presentation can be surpris- ingly subtle, there has to be a low threshold for further investigation, and this generally takes the form of cerebrospinal fluid (CSF) analysis com- bined with cross-sectional imaging. Although recent advances in polymerase chain reaction (PCR) CSF analysis have increased the ability to make a specific diagnosis, a large part of the diagnostic process still relies on radiological interpretation. MRI is the modality of choice owing to its higher sensitivity of lesion detection and superior contrast resolution compared with CT. Nevertheless, the ready availability of CT allows it to remain a first line investigation, typically in the form of a screening tool prior to lumbar puncture. There is a considerable overlap of imaging features between the various disease subtypes; therefore, a systematic approach to interpretation is essential. Since MRI is the mainstay of investigation of the CNS in AIDS, this review concentrates on the MRI appearances. It aims to simplify the process of radiological analysis by categorizing the various patterns of disease and highlighting the main differential diagnoses for each pattern.
... The utility of FLAIR imaging relates to its sensitivity in depicting lesions causing T2 prolongation against a suppressed CSF background. The superiority of FLAIR imaging as compared with T1-and T2weighted imaging has been suggested in the evaluation of a variety of disorders, such as stroke (4), multiple sclerosis (5), infections (6), hypertensive ᭧ American Society of Neuroradiology encephalopathy (7), and cerebral hemorrhage (8). One of the major limitations of FLAIR imaging, however, is ventricular CSF pulsation artifact (VCSFA) (3). ...
CSF pulsation artifact is a pitfall of fast fluid-attenuated inversion-recovery (FLAIR) brain MR imaging. We studied ventricular CSF pulsation artifact (VCSFA) on axial FLAIR images and its relationship to age and ventricular size.
Fast FLAIR axial images were obtained on a 1.5-T unit (8000/150/2 [TR/TE/ excitations], inversion time = 2200, field of view = 24 cm, matrix = 189x256, and 5-mm interleaved sections). Two observers rated VCSFA (hyperintensity on FLAIR images) in the lateral, third, and fourth ventricles by using a three-point ordinal scale in 100 consecutive subjects (ages 20-86 years) with normal brain MR studies. Left-to-right third ventricular width was also measured.
Seventy-two subjects had VCSFA in at least one ventricular cavity. The fourth ventricle was the most common site of VCSFA (n = 58), followed by the third ventricle (n = 47) and the lateral ventricles (n = 13). VCSFA was usually severe in the third and fourth ventricles and less severe in the lateral ventricles. Fourth ventricular VCSFA was significantly associated with third ventricular VCSFA. Increasing third ventricular size and, to a lesser extent, increasing age was significantly associated with VCSFA. Ghost pulsation of VCSFA occurred across the brain parenchyma in the phase-encoding direction. VCSFA seen in the fourth ventricle on axial FLAIR images disappeared on sagittal FLAIR images in one subject.
VCSFA on axial FLAIR images represents inflow artifact caused by inversion delay and ghosting effects. VCSFA might obscure or mimic intraventricular lesions, especially in the third and fourth ventricles. Although common in adults of all ages, VCSFA is associated with advancing age and increasing ventricular size. Thus, altered CSF flow dynamics that occur with ventriculomegaly and aging contribute to VCSFA on axial FLAIR MR images.
... The superiority of FLAIR relates to its sensitive detection of lesions causing T2 prolongation with nulling of normal CSF background, leading to high lesion/tis-sue contrast (4). The usefulness of FLAIR as compared with T1-and T2-weighted MR imaging has been shown in association with a host of brain diseases, including stroke (4,5), multiple sclerosis (6,7), infections (8,9), hypertensive encephalopathy/ reversible posterior leukoencephalopathy syndrome (10), and myotonic dystrophy (11). In addition, one group has shown that FLAIR imaging may be reliable in the diagnosis of acute SAH and may be superior to CT in this regard (12)(13)(14). ...
Fluid-attenuated inversion-recovery (FLAIR) MR imaging may show subarachnoid hemorrhage (SAH) with high sensitivity. We hypothesized that the FLAIR technique is effective and reliable in the diagnosis of cerebral intraventricular hemorrhage (IVH).
Two observers evaluated the 1.5-T MR fast spin-echo FLAIR images, T1- and T2-weighted MR images, and CT scans of 13 patients with IVH and the FLAIR images of 40 control subjects.
IVH appeared bright on the FLAIR images obtained during the first 48 hours and was of variable appearance at later stages. FLAIR MR imaging detected 12 of 13 cases of IVH; no control subjects were falsely thought to have IVH (92% sensitivity, 100% specificity). However, IVH could not be fully excluded in the third ventricle (20%, n = 8) or in the fourth ventricle (28%, n = 11) on some control images because of CSF pulsation artifacts. Two cases had CT-negative IVH seen on FLAIR images. One case had FLAIR-negative IVH seen by CT. Although the sensitivities of conventional MR imaging (92%) and CT (85%) were also high, FLAIR imaging showed IVH more conspicuously than did standard MR imaging and CT in 62% of the cases (n = 8). FLAIR was as good as or better than CT in showing IVH in 10 cases (77%). FLAIR images showed all coexisting SAH.
FLAIR MR imaging identifies acute and subacute IVH in the lateral ventricles with high sensitivity and specificity. In cases of subacute IVH, conventional MR imaging complements FLAIR in detecting IVH. The usefulness of the FLAIR technique for detecting third and fourth ventricular IVH may be compromised by artifacts. Blood hemoglobin degradation most likely causes the variable FLAIR appearance of IVH after the first 48 hours.
